Subscribe to our free daily newsletters
. 24/7 Space News .

Subscribe to our free daily newsletters

Herschel Scopes Best Candidate For A Supernova Explosion

Artist's impression of Rho Cassiopeiae at the 2000 outburst. Upper right: Spectral line profiles. Bottom right: Light curve. Picture credit: Gabriel Pérez Díaz and the Instituto de Astrofísica de Canarias.
Santa Cruz - Feb 11, 2003
An international team of astronomers using the Utrecht Echelle Spectrograph on the William Herschel Telescope has identified the bright star Rho Cassiopeiae as the best candidate to undergo a supernova explosion in the near future. The results of this investigation are to be published in a research paper in The Astrophysical Journal on February 1.

Rho Cassiopeiae is one of the brightest yellow "hypergiant" stars in the Milky Way. In spite of being 10,000 light-years away from the Earth, this star is visible to the naked eye as it is over half a million times more luminous than the Sun.

Yellow hypergiants are rare objects; there are only 7 of them known in our Galaxy. They are very luminous and have surface temperatures between 3,500 and 7,000 degrees. It is believed that these stars are at a very evolved stage of their life and will ultimately explode as supernovae.

Yellow hypergiants are peculiar stars because they display an uncommon combination of brightness and temperature, which places them in a so-called Yellow Evolutionary Void.

When approaching the Void these stars may show signs of peculiar instability. Theoretically, they cannot cross the Void unless they have lost sufficient mass. During this process these stars end up in a supernova explosion: their ultimate and violent fate. The process of approaching the Void however, has not yet been studied observationally in sufficient detail as these events are very rare.

The highly efficient Utrecht Echelle Spectrograph has allowed astronomers to monitor Rho Cassiopeiae in detail from 1993 to 2002. The observations were aimed at investigating the processes occurring when yellow hypergiants approach and bounce against the Yellow Evolutionary Void, and the results revealed almost regular variations of temperature within a few hundred degrees.

However, what happened with Rho Cassiopeiae during the summer of 2000 went beyond anybody's expectations.

The star suddenly cooled down from 7,000 to 4,000 degrees within a few months. Astronomers discovered molecular absorption bands of titanium-oxide (TiO) formed in the slowly expanding atmosphere, suggesting that they had witnessed the formation of a cool and extended shell which was detached from the star by a shock wave carrying a mass equal to 10% of our Sun or 10,000 times the mass of the Earth. This is the highest amount of ejected material astronomers have ever witnessed in a single stellar eruption.

The outburst was similar to the shock wave a jet aircraft produces, which can be heard as a sonic boom. Gas rushed outwards at four times the speed of sound.

Dr. Garik Israelian, one of the members of the discovery team, said: "Rho Cassiopeiae could end up in a supernova explosion at any time as it has almost consumed the nuclear fuel at its core.

"It is perhaps the best candidate for a supernova in our Galaxy and the monitoring of this and other unstable evolved stars may help us to shed some light on the very complicated evolutionary episodes that precede supernova explosions."

Rho Cassiopeiae experienced periods of excessive mass loss in 1893 and around 1945, that appeared to be associated with a decrease in effective temperature and the formation of a dense envelope. The results suggest that Rho Cassiopeiae goes through these events every 50 years approximately.

Since the event in the year 2000, Rho Cassiopeiae's atmosphere has been pulsating in a strange manner. Its outer layer now seems to be collapsing again, an event that looks similar to one that preceded the last outburst.

The researchers think another eruption, possibly a stronger one, is imminent.

Dr. Israelian comments: "Given the large distance it is possible that Rho Cassiopeiae has already exploded and become a black hole or a neutron star. In 10,000 years the star will undergo 200 outbursts (if the frequency is 50 years). In each event it will lose 0.1 times the mass of the Sun and therefore 20 solar masses will be lost in 10,000 years! Very likely Rho Cassiopeiae does not exist any more."

The science team involved in this research consists of Drs. Alex Lobel, Andrea Dupree, Robert Stefanik and Guillermo Torres (CfA, USA), Garik Israelian (Instituto de Astrofísica de Canarias, Spain), Nancy Morrison (University of Toledo, USA), Cornelis de Jager and Hans Nieuwenhuijzen (SRON, The Netherlands), Ilya Ilyin (University of Oulu, Finland) and Faig Musaev (SAO, Russia).

Related Links
William Herschel Telescope
Isaac Newton Group of Telescopes
Search SpaceDaily
Subscribe To SpaceDaily Express

Earth Likely Spared From One Form Of Cosmic Doom
Greenbelt - Jan 13, 2003
We have one less thing to worry about. While the cosmic debris from a nearby massive star explosion, called a supernova, could destroy the Earth's protective ozone layer and cause mass extinction, such an explosion would have to be much closer than previously thought, new calculations show.

Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once

credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly

paypal only

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.